Thermotelephone transmitter and receiver



ROBERT AERNOUT BARON VAN LYNDEN.

THERMOTELETPHONE TRANSMITTER AND RECEIVER.

APPLICATION FILED MAR; 12. 1918.

Patented Oct. 10, 1922.

R05IA7720lll Bar-012 2km [vmielz INVENTOR.

as electrical ones instance the bow liable to lean or fall mm starts tartar ROBERT AERNOUT Berton van L iti'nsnn ASSIGNMENTS,

MEhldti tr i ch...

YNIDEN, 0F UTRECHT, NETHERLANJDSQA$SIGNOfi BY 'IOQQJEKIERIGAN THERIEGPHONE COMPANY, OF BOSTON,

"MASSACHUSETTS, A. OOBPGRATION OE MASSACHUSETTS.

. rnnnntornrnrnonn TRAN Application as March 1a, 1918.

To all whom it may concern Be it own that I, ROBERT 'AERNOUT BARON VAN LYNDEN, a subject of the Queen of the Netherlands, and resident of Utrecht,

in'the Province of Utrecht and Kingdom of the Netherlands, have invented certain new and useful Improvements in Thermotelephone Transmitters and Receivers, of which the following It is well-known that phones, that is to say, transmitters and receivers structure a ductors, or hot wires,

is a specification.

sdcalled thermothermo-telephone embody in their number of extremely thin conusually shaped as small bows or loops standing erect and'securedto a support or loops of the same cross energy consumed by each pends on its length, and

carrier.

section, the electric With wire bow or loop dethis energy in turn, in the case of a thermo-telephone, determines the loudness of sound-reproduction.

nthe other hand, in order satisfactory or most duction, 1t is necessary that to obtain a efficient sound-reproa certain amount of electric energy be developedin the hot wires in the form of Joule-heat. From this 1 it follows that, for a given cross section of the hot wire, which be best.

there is a it becomes too weak place points of the or slack, and

over to one slde, 1n posltionit may come in conresult from definite length at the sound-reproduction results will iowever, mechanical conditions as well .afiect the results. If for or loop is made too high,

w or loop. No this if such at equipotential different loops, but 1n practice it cannotvery well be avoided that such contact should occur, at of different potential.

times, between points In this event one of the loops would become over-loaded, since the loops are connected in parallel, and the loop thus receivlng an excess of current would become incandescent, and the intermittent contact impair the correct sound. referred to might indeed be ing the loops be objectionable, both on a farther apart, but this resulting therefrom would reproduction of the The danger of mutual contact justv avoided by spacwould ccount of the increased size of the apparatus, which would make it less convenient in use, and I on acwill be 1 sivrrrrnn earn nncnivna.

Serial No. 222,016.

that sound-reproduction apparatus or containers coating may be various ways, as by dipping suitable bath, by heating them to produce a superficial oxidation, by the Schoop spraying process, or in any other suitable manner, as long as the treatment results in the production of a fine skin or coating of'satisfactory insulating power and of proper resistance to the effects of the temperature to which the hot wire is subjected during the operation of the thermophone.

Practical trials have shown that the presence of an insulating skin or coating made according to my invention does not affect the sound-reproducing properties of the hot wire.

Among the numerous advantages of my invention, there is, first, the fact adjoining oops or bows may touch each other without causing trouble by short-circuiting, and from this it follows that the loops may be placed closer together than according to present constructions, where the loops are placed at a relatively considerable distance from each other, in order to minimize the of the container (J remaining unaltered.

When the container C is made of metal or other conductor of electricity, and the loops might come in contact with the container, it is desirable, for additional safety, to apply an insulating coating C of the character referred to, upon those partsor surfaces of the container which are liable to be engaged by the loops.

It is not necessary that the coating be non-conductive at the time of its formation or application, since I may apply a conmetal (platinum).

2 marine ducting coating and convert it into a nonconducting one. For instance, I may deposit on the hot wires, by electrolysis, an extremely fine coating of a suitable metal, say copper, and while this coating will be conducting at first, the heat developed in the wire during the operation of the appa- "atus will quickly convert the copper or other metal into a non-conducting oxid, eflicient to form an insulating sheath or protector for the purposes of my invention.

Another important advantage ot' my invention resides in the possibility of using non-precious metals for the hot wire, which hitherto has always been made of precious The insulating coating or skin, whether formed by superficial oxidation or otl'ierwise, will prevent access of the surrounding air to the hot wire proper, so that no oxidation of the core or hot wire proper need to be feared. The wider choice of materials available for the hot wire is a great advantage of my invention, since the materials employed hitherto are not always as efiicient as might be desired, and in particular, the character of transmission is often rather poor on short lines. The reason for this is found in the fact that, in a short line, the resistance of the thermo-telephone is comparatively large in relation to the resistance of the line. The materials used hitherto tor the hot wires, via: precious metals, have a positive temperaturecoefiicient, that is to say, their specific resistance increases with the current-density, a d thus, the heating effect still further increases the proportion which the resistance of the thermo-telephone forms of the total resistance (telephone and line), thus accounting for the comparatively unfavorable results often observed on very short lines. The tops of the current-oscillations or current-waves are flattened by this increased resistance, and this alteration of the waves is prejudicial to the purity of the sound reproduced. Among non-precious metals, however, there are some (for instance the alloy imown as constantan) the temperature-cost icient of which is practically negligible, that is to say, their specific resistance is not afiected materially by the increase in temperature, hence the possibility of using non-precious metals is an advantage not only on account of the relative cheapness of such metals, but for the reason that, by the employment of materials having a low or negligible temperature-coetficient, a material improvement in soundreproduction may be obtained, particularly on short lines.

Various modifications may be made without departing from the nature of my invention as set forth in the appended claims.

I claim:

1. A thermophone, provided with a hot wire having an insulating coating in contact with atmospheric air.

rir thermophone, provided with a hot wire having an insulating coating, .and a container for said hot wire having an insulating coating at the point or points liable to come in. contact with said hot wire.

3. A thermophone, provided with a metalbe hot wire having a fine coating of a metal in contact with atmospheric air adapted to become superficially oxidized upon the heat ing or such wire.

A thermophone, provided with a hot wire having a fine coating of copper in contact with atmospheric air.

A thermophone, provided with a hot wire made of a material havinga practically rr' igible temperature-coefiicient, and coated externally with an insulating material in contact with atmospheric air.

6. rl. thermophone, provided with a hot wire, and a conducting container for said hot wire, said container having an insulating coating at the point or points liable to come in contact with said hot wire.

in testimony whereof I have hereunto set my hand.

nearer AERNUUT BARN-l van LYNDEH. 

